Injectors and hydrokinetic amplifiers, such as shown in U.S. Pat. No. 4,569,635, are constant flow devices that can operate between minimum and maximum pressures at a single flow rate. To operate near maximum pressure requires careful matching of the output pressure resistance with the pressure and flow capability of the hydrokinetic amplifier. If vapor pressure then drops, which can easily happen in an industrial environment placing other demands on the same vapor supply, the amplifier has insufficient motivating vapor to meet the output pressure resistance and stalls. This stops the outflow, dumps the inflow, and requires a restart. A sudden increase in liquid supply pressure can also cause a stall by supplying more liquid than the available vapor can accelerate through the output of the amplifier. Since fluctuations in liquid and vapor supply pressures are bound to occur, hydrokinetic amplifiers are usually designed to operate with less than optimum inputs, but this has the disadvantage of reducing the output performance, even when optimum inputs are available. These limitations make injectors and hydrokinetic amplifiers more difficult to match with output pressure resistances than centrifugal pumps, for example, which can vary the flow rate, as well as the pressure, of their outputs.
We have discovered a way of providing a hydrokinetic amplifier with a variable output flow rate, allowing it to better accommodate variations in inflow rates and in output pressure resistances. Our way of varying the outflow rate from a hydrokinetic amplifier surprisingly improves the efficiency of its diffuser so that hydrokinetic amplifiers provided with our invention can increase the product of the pressure and volume of their output. Our variable outflow rate can also be used for controlling the temperature of the output or the proportion of two flows combined into the output. This includes starting and stopping the flow of an additive material, such as a detergent or foaming agent, that can merge with the output flow, when desired by an operator. Our invention accomplishes improved efficiency and a variable output flow rate in a simple and inexpensive way that makes hydrokinetic amplifiers more versatile without adding significantly to their cost.